The prior art has disclosed what are known as flat-panel image detectors for the detection of X-rays. Flat-panel image detectors of this type are used in particular in digital radiography. Flat-panel image detectors have a scintillator layer produced, for example, from CsI:Tl or from Gd2O2S:Tb, which has been applied to a photodiode array formed from photodiodes.
To achieve a desired image resolution, the scintillation light should be recorded only by that photodiode which is located precisely vertically beneath the position at which the scinitillator light is generated. In practice, however, depending on the formation of the microstructure of the scintillator layer, more or less pronounced crosstalk occurs in the scintillation light from the position at which it is generated to adjacent photodiodes. To improve the spatial resolution of flat-panel image detectors of this type, it is desirable to reduce or even minimize the crosstalk.
Scintillator layers produced from Gd2O2S:Tb are homogenous and laterally unpatterned in form. They are generally approximately 200 μm thick. To prevent extensive lateral propagation of the scintillation light, it has been attempted to reduce the thickness of the scintillator layer. However, this in turn disadvantageously leads to the X-radiation which is incident on the scintillator layer not being completely absorbed, which has an adverse effect on the quantum efficiency of a flat-panel image detector of this type.
Scintillator layers produced from CsI:Tl generally include fine acicular crystals which are oriented parallel to the direction of incidence of the X-radiation and have a diameter of generally from 5 μm to 10 μm. The scintillation light which is generated in such crystals generally propagates in accordance with the orientation of the crystal and is to a large extend transmitted to the photodiode below. Nonetheless, in this case too, crosstalk of some of the scintillation light with adjacent photodiodes occurs. Finally, scintillator layers produced from CsI:Tl have the drawback of being hygroscopic, and consequently they have to be effectively protected from atmospheric humidity.